Cellulosic textiles protected against mildew



CELLULOSIC TEXTILES PROTECTED AGAINST MILDEW Frederick J. Meyer,Freeland, Mich., assignor to The Dow Chemical Company, Midland, Mich., acorporation of Delaware No Drawing. Application April 26, 1947, Serial N0. 744,157

5 Claims.

This invention relates to cellulosic textile materials, the surface andfibers of which exhibit increased resistance to mildew and rot, and to atreatment whereby such increased resistance may be imparted tocellulosic textiles. It relates in particular to the treatment of cottontextiles and to the treated product.

The problems arising from the mildewing and rotting of cellulosictextiles, especially those which are exposed to the weather in Warmhumid climates, have long been known. Many materials have been proposedand used to protect cotton cloth and similar textiles from mildew, withvarying degrees of success. It has been observed that some of thetreating agents are too fugitive to give the desired prolongedprotection. Others, have a limited application because of their toxic orirritant character which requires them to be handled with caution. Ofequal importance is the discovery that even the more permanent and leastirritating agents used to increase the resistance of cotton textiles tofungus growth have been defective in the protection afforded to thecloth against various weakening or tendering influences. Thus, samplesof the treated cloth have been capable to prolonged exposure in humidtropical climates without supporting mold growth, but have becomeprogressively weaker until the cloth has little residual strength. It isnow recognized that a satisfactory protectant for such cellulosictextiles should permit them to retain their strength as well aspreventing the growth of fungi.

It is accordingly an object of the present invention to provide acellulosic textile product, the surfaces and fibers of which carry anagent to increase the resistance of such textile to mildew and tominimize loss of strength of the textile during prolonged Weathering. Arelated object is to provide a method of treating cellulosic textiles,such as cotton, linen, ramie, hemp, sisal, jute and the like, to givethem increased resistance to mildew and increased retention of strengthon ageing. Other and related objects may appear hereinafter.

I have found that the desired results are obtained to a remarkableextent when cellulosic textiles are treated to contain, on theirsurfaces and in their fibers, an effective fungistatic quantity which iscommonly from about 1 to about 5 per cent by weight (more or less) of2,4-dihydroxybenzophenone or certain substitution products 2 thereof,and that the treated product is unique in the degree of its retention ofstrength under normally weakening conditions of exposure. Thesubstitution products of 2,4-dihydroxybenzophenone which have been foundto be operative, and which may be used in the present invention are themonochloroand dichloro-2,4'-dihydroxybenzophenones, and the 4-methyland5-methyl-2,4-dihydroxybenzophenones. Mixtures of the named substitutionproducts with one another or with 2,4-dihydroxybenzophenone are alsoeffective materials for use in the invention, as are mixtures of atleast 50 per cent of 2,4-dihydroxybenzophenone with the isomeric butindividually ineffective or less effective hydroxybenzophenones whereinthe hydroxyl groups are in the 2-, 4-, 2,2'-, 3,3'-, 3,4.--, orUP-positions.

. The positions occupied by chlorine atoms in the mononones contemplatedfor use in the invention are not known, but the compounds found usefulare those which are obtained by direct chlorination of the designateddihydroxy compound until the chlorine content reaches a value from about14 to about 25 per cent. An under-chlorinated product, containing lessthan 14 per cent chlorine, consists essentially of2,4-dihydroxybenzophenone and its mono-chloro derivative, and may beused effectively. Similarly, a slightly overchlorinated product, havinga chlorine content, for example, of about 30 per cent, consist of amixture of some unchlorinated, some mono-chloroand sometrichloro-2,4'-dihydroxybenzophenone together with a preponderant amountof the desired dichloro-compound, and is also effective as an agent toprotect cellulosic textiles against attack by mildew and rot withoutitself causing deterioration of the cloth.

The above-described protective agents may be applied to the textilematerial by any of several procedures. The most convenient methodcomprises dissolving the 2,4-dihydroxybenzophenone or substitutionproduct thereof to form a standard solution in a volatile organicsolvent, dipping the cloth in the solution, expressing any excess ofsolution over that which contains the desired amount of anti-fungusagent, and evaporating residual solvent. This leaves a deposit of theagent in and on the fibers. In commercial practice, the speed at whichthe cloth passes through the bath is adjusted so that a constant weightof solution is absorbed, and the amount of protecanddichloro-ZA-dihydrobybenzophetive agent carried out of the bath isdirectly proportional to its concentration in the bath.

In another procedure, the dihydroxybenzophenone compound, of the groupdefined, may be dissolved, as described above, using a solvent which isimmiscible with water, and the resulting solution may be emulsified asthe disperse phase in an aqueous medium and applied to the cloth as anemulsion. Subsequent drying deposits the agent in the cloth. Similarly,the protective agent may be dispersed in, and deposited on the clothfrom a liquid sizing material such as a starch dispersion.

Since a large proportion of the cloth which is given commercialanti-fungus treatment is of the water-repellent type, intended fortents, awnings, tarpaulins, sails, and the like, it is convenient toapply the dihydroxybenzophenone compound to the cloth from the bath usedto impart water repellency. If the water-repellent is a lacquer type ofsolution of a film-forming material, the present agents may be dissolvedtherein. If the water-repellent is or comprises a wax emulsion, thepresent agent may be dissolved in a suitable solvent, emulsified withwater, and mixed in the desired proportions with the wax emulsion beforeapplication to the cloth. A particular wax-containing, film-formingsolution for imparting water repellency, and which is referred to insome of the following examples as the binder, is composed of 15 parts byweight of a low viscosity type of ethyl cellulose (48.5 per cent ethoxylcontent) 10 parts of castor oil, 25 parts of hydrogenated rosin, and 50parts of microcrystalline Wax, dissolved in a mixture of 85 per cent byvolume of a hydroformed, i. e. cracked and hydrogenated, petroleumnaphtha high in cyclic hydrocarbons, and 15 per cent by volume ofbutanol. To this solution is added the benzophenone derivative, prior tothe cloth treating operation. The deposited solids thus contain both thewater repellent binder and the anti-fungus agent.

It is a necessary condition that a chemical, to be capable of successfuluse as an anti-fungus agent in textiles, must show efiective control ofthe commoner mildew and cellulose rotting organisms in laboratory testsusing pure cultures; it must have low volatility and a degree ofthermostability to favor permanence of the material in treated textiles;and, it must show positive control of air-and soil-borne organisms inoutdoor exposure tests of treated textiles under con ditions to whichsuch textiles may be subjected in use. In preliminary tests, each of theabovenamed compounds (2,4'-dihydroxybenzophenone and its namedsubstitution products) was found to be effective as a fungistat in pureculture laboratory tests on inorganic salts agar in petri dishes at 30C. using various known air-and soil-borne fungi. When samples of cottoncloth were treated to contain from 1 to 5 per cent by weight of the same2,4 dihydroxybenzophenone compounds, and were inoculated with the samecultures and subjected to a humid atmosphere at 30 0., equally goodfungistatic action was noted. The compounds were each found to be asstable and to have at least as low volatility as any of the phenolictypes of fungistatic agents commercially sold for the present purpose.The permanence of these compounds in cotton textiles was noted by theircontinued effectiveness after the treated textiles were subjected toultra-violet radiations in a Fadeometer for 552 hours (23 days). Thetest organisms, which were controlled both before and after Fadeometerexposture, were Aspergillus niger and Chaetomzum globosum, the latterbeing a cellulose rotting organism. The favorable results in thesepreliminary tests justified further tests under more practicalconditions, including the soil burial and field exposure tests reportedin subsequent examples.

Example 1 Cotton duck (No. 10) was treated with solutions of thecompounds listed in the following table, under conditions to deposit inthe dried cloth the indicated weights of the respective agents. Samplesof the cloth were buried in moist soil for the indicated periods oftime, and were then tested to determine the per cent retention ofbreaking strength. This gives an index of the efiectiveness of thetreating agents against soilborne cellulose rotting organisms. Forcomparison, similar tests were run using certain isomeric, butapparently ineffective, dihydroxybenzophenones, and other tests werecarried out using the commercial fungistat,dichlorodihydroxydiphenylmethane.

Per Cent Retention of Per Cent Breaking Strength Compound Wgiy ht afterSoil Burlal for on Cloth 21 days 42 days 56 days A None 0 0 0 B2,4'-dihydroxy-benz phenone 1 100 97 2 100 3 100 100 Dhydroxybenzophenone 1 100 100 100 Do 2 100 93 100 E2,4-dihydroxy-4-methylbenzophenone 2 1 88 F2,4'-dihydroxy-5-methylbenzophenoue 2 1 100 G 60 parts B. 30 parts E, 10

parts F 1 l 100 90 For comparison H 2,4"-dihydroxy-5-methylbenzophenone2 1 13 I 3,4-dihydroxy benzephenone 1 13 0 0 Do 2 17 0 0 Do 3 l5 0 13 J3,3-d ihydroxy -benzophenone 1 25 0 0 Do 2 57 14 14 Do 3 50 14 0 KDichlorodihydroxy-dlphenylmethone. 1 100 92 89 Do 2 100 100 92 3 99 99 114 days.

Other samples of the same treated cloths were inoculated with purecultures of C. globosum and A. niger, and yet another series was firstexposed in a Fadeometer for 23 days and then inoculated with theseorganisms. Time was allowed for growth of the organism, afterinoculation. The following observations were made as to the extent ofgrowth of the test organisms. The samples are identified by the lettersappearing at the left in the preceding table.

In the tables to follow, the various degrees of fungistaticeffectiveness are indicated by the following conventional symbols:

0=no growth +=slight growth ++=moderate growth +++=heavy growth++++----very heavy growth Mildew Readings Compound 0123:: Not IrradiatedIrradiated 23 Days 2 A. niger 2,25? A. m'qer Example 2 Several of thecompounds reported in Example 1 were dissolved in the previously definedwaterrepellent binder and were applied to cotton duck so that the clothcontained 2 per cent each of the anti-fungus agent, the film-formingconstituents of the binder, and microcrystalline wax. The treated clothsWere buried in moist soil, as before, and a measurement was made todetermine the per cent retention of breaking strength after the variouslengths of exposure listed in the following table.

Per Cent Retention of Breaking Strength after Burial for- Compound 14days 28 days 42 days 56 days Binder only 0 0 0 0 B 100 83 99 96 106 86100 25 100 88 100 34 26 21 14 65 37 29 0 92 99 100 99 It may beconcluded that the water-repellent binder exerts no significantinfluence upon the fungistatic effectiveness of the compounds tested.Example 3 Practical weathering tests on treated cotton fabrics werecarried out for periods of three, six, nine and twelve months, beginningeach year in March, in the sub-tropical climate of the coastal plainwithin a few miles of the Gulf of Mexico in southern Louisiana. Thecloth samples were mounted on racks facing south and tilted at an angleof 60 with the ground in an open field. After exposure for the statedperiods, an observation was made to determine the extent of any mildewgrowth, and a measurement was made to determine the per cent loss inbreaking strength, an index of the combined extent of rotting and oftendering of the cloth due either to weathering action or to thechemical, or both.

Visual Observations for Mold Growth Per Cent Retention of Breaking PerCent Binder, Strength after Compound Flnunogllgitgt 012g; 3 M onths 6Months Exposure for- Front Back Front Back 3 Months 6 MonthsControl-cloth alone 0 0 76 62 Controlc1oth and binder 0 4 0 662,4-dihydroxybenzophenone 1 4 0 78 51 Do. 2 4 0 O 0 78 56 3 4 0 0 0 59 1O 0 75 50 2 0 O 0 0 60 3 0 0 0 0 0 84 66 1 4 0 0 73 53 2 4 0 0 77 48 3 40 0 0 76 56 1 0 0 0 76 54 2 0 0 0 81 63 3 0 0 0 0 0 83 61 1 4 0 0 71 512 4 0 0 0 71 49 3 4 0 0 0 73 57 1 0 0 78 60 Do 2 0 0 84 67 Do 3 0 0 0 8371 50-50 mixture of 2,4- and 4,4'-dihydroxybenzophenone 2 4 0 64 45 Do 34 0 64 47 Do. 4 4 0 0 64 44 Do 2 0 73 61 Do"..- 3 0 0 0 H 71 53 Do 4 0 00 71 51 For comparison 2,2-dDihydroxybenzophenone3-3-dihydroxybenzophenone 3-4-d ihydroxybenzophenone- Do2-hygroxy-5-chlorobenzophenon o Dih bdroxydichlorodiphenylmethan Do.Copper naphthenate (1% Cu) o Phenyl mercuric chloriri a 3 4 0 0 67 44 30 0 84 51 2 4 66 2 4 63 2 4 0 52 35 3 4 52 38 4 4 0 52 31 2 0 H- 4-H 753 3 O -H- +44- 74 4 4 0 71 49 3 4 0 0 66 49 3 0 0 0 89 56 1 4 0 H 76 512 4 0 0 71 48 3 4 0 0 0 55 33 1 0 0 67 51 2 0 0 0 58 38 3 0 0 0 46 25 14 0 0 O 0 49 23 1 0 0 0 0 0 58 28 2 4 51 37 2 0 61 32 The same relativeorder of effectiveness was noted at the end of twelve months.

It is observed from the foregoing data that 2,4-dihydroxybenzophenone,its 4-methyl and 5-methyl analogs, and its monoand dichlorosubstitutionproducts are at least as effective in controlling mildew formation oncotton cloth as are many of the commercial fungistats recommended forthis purpose. It is also observed that the treated cloth of the presentinvention retains its strength to a much greater extent than does clothtreated with any of the usual fungistats. In many cases the time rate ofdecline of the tensile strength of the present treated fabric is lessthan half of that normally encountered with other fungistats. This isindicative of a prolongation of the useful life of the cloth, whentreated in accordance with the present invention. It is noted that, withmany common fungistats, an increase in the amount of fungistat in thecloth is accompanied by a decrease in the strength of the cloth, butthat, in contrast thereto, an increase in the amount of the presentprotective agents induces no decrease and often is accompanied by agreater retention of tensile strength of the treated fabrics.

The invention has been illustrated with reference to the protection ofcotton duck, but is not so limited. The indicated advantages accrue toany cellulosic textile containing the present protective agents, and itis immaterial Whether the textile is a woven cloth, a thread, a yarn, arope, or a net, of cotton, linen, jute, hemp, sisal, or other cellulosicfiber.

The agents here employed for the preservation of cellulosic textiles maybe used as well to protect other susceptible materials, including paper,

wood veneers, adhesives and sizes from attack by mildew.

I claim:

1. A fibrous cellulosic textile product, the surfaces and fibers ofwhich carry from about 1 to about 5 per cent of a material from thegroup consisting of 2,4'-dihydroxybenzophenone, the monoanddichloro-derivatives thereof, the 4- methyl and 5-methyl analogsthereof, and mixtures of said compounds.

2. Cotton cloth, the surfaces and fibers of which carry from about 1 toabout 5 per cent of a compound from the group consisting of 2,4-dihydroxybenzophenone, the monoand dichloroderivatives thereof, thel-methyl and 5-methyl analogs thereof, and mixtures of said compounds.

3. Cotton cloth, the surfaces and fibers of which carry from about 1 to5 per cent of 2,4- dihydroxybenzophenone.

4. Cotton cloth, the surfaces and fibers of which carry from about 1 toabout 5 per cent of a chlorinated 2,4-dihydroxybenzophenone consistingprincipally of the monoand dichloroderivatives.

5. Cotton cloth, the surfaces and fibers of which carry from about 1 toabout 5 per cent of a mixture of 2,44-dihydroxybenzophenone and itsl-methyl and 5-methyl analogs.

FREDERICK J. MEYER.

REFERENCES CITED The following references are of record in the file ofthis patent:

Marsh et al.: Ind. Eng. Chem., July 1946, vol. 38, pp. 701-5.

AMI

